For ultimate nutritional value, you will want to gut-pack them before feeding them. Feed them a high-quality food soaked in a vitamin supplement such as Boyd's Vita-Chem about an hour before you feed them to your lotl.

You are definitely right to be suspicious of the feeder guppies in pet stores. They are kept in crowded conditions with minimal care and most likely have parasites. >.<

Always be suspiscious of pet store fish. :D That is what I've learnt here on forums :D now I'm a paranoid person that goes to the store, eyes the fish and thinks "I know where you've been or do I??"

The pet I'm trying to feed is an axolotl, there is only two types of feeder fish I'm interested in. Wild or feeder guppies and Minnows, because they are small enough, easy to breed and make a nice meal for him.

Easter mosquito fish or western mosquito fish prefer cold water and will will probably give your Anoxtol a bit of a chase.

I chose the fish that I have available near me at the moment, or that I can find, besides lotls are slow, at least mine is. Unless they swim near his head he won't catch it. I've been trying to see if he would eat the amano shrimp lol.

Axolotls don't go around chasing their food, they are oportunistic hunters, staying hidden and when food swims by WHAM, sucked in.

I decided to go with minnows-- though I have a small school in his tank and he doesn't bother them XD though I do feed him well.